The objective of the proposed project is to establish and operate a Data Coordinating Center in support of a multicenter randomized clinical study, the Prism Adaptation Trial. Prism adaptation is an adjunct procedure to surgery for the correction of acquired esotropia. The goals of the proposed trial are to determine: 1. Whether there is an overall beneficial effect, in terms of small post-operative angles of deviation and binocularity of vision, of the prism adaptation procedure; 2. Whether the patients who respond to prism adaptation are more accurately corrected by operating for the prism-adapted angle or for the original angle of deviation; 3. Whether patients who respond to prism adaptation by developing a new stable angle of deviation have a better surgical result than those who do not respond; and 4. Whether certain input variables are useful in predicting which patients are more likely to benefit from prism adaptation. To answer these questions a double randomization study has been designed. Three-fifths of patients will be randomly selected to go through prism adaptation prior to surgery. The other two-fifths will have surgery based on the amount of crossing measured using standard examination techniques. Of those patients who respond to prisms, one-half will have surgery based on the amount of prism required to stabilize the deviation, while the rest will have surgery based on the amount of crossing originally measured. The Data Coordinating Center will play a central role in the Trial, being responsible for statistical design, protocol development, standardization of procedures, forms design and printing, training of clinic personnel, data processing and quality control, monitoring of patient recruitment, data accrual, adherence to protocol, endpoints, and adverse effects, and statistical analysis of results. The research plan in this proposal specifies the methods which will be used to carry out these responsibilities.